Compact Dual-band Bandpass Filter Research Articles

Compact dual-band bandpass filter with good frequency selectivity

A compact microstrip dual-band bandpass filter with controllable bandwidth for each passband and good frequency selectivity is proposed. The proposed dual-band bandpass filter has five transmission zeros. The transmission zeros are generated by each dual-mode resonator and input/output port cross-coupling. The dual-band bandpass filter application is designed for 2.4/5.2 GHz WLAN. Experimental measurements are presented to validate the theory.

Dual-band bandpass filter using dual-mode resonators

A compact microstrip dual-band bandpass filter (DBBPF) with controllable bandwidth for each passband is proposed. Each passband is independently designed using two different dual-mode resonators. The proposed DBBPF has three transmission zeros. Two transmission zeros are generated by each dual-mode resonator. An additional transmission zero is generated by input/output port coupling. The DBBPF application is designed for 2.4/5.7 GHz WLAN. Experimental measurements are presented to validate the theory. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2515–2517, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26355

Design of a Compact Dual-Band Bandpass Filter Using Opposite Hook-Shaped Resonator

In this letter, a compact dual-band bandpass filter is presented for wireless area networks (WLAN) operations. The filter, which is only 0.04 λ0 × 0.09λ0 in overall dimensions, is composed of two symmetric parts. In each part, two opposite hook-shaped strips with different resonant paths are used to achieve the dual-band operation at 2.4 and 5.8 GHz, with 19.54% and 15.12% fractional bandwidth, respectively. The central frequencies of the two passbands can be controlled independently by adjusting dimensions of the hooks. To verify the proposed idea, a prototype is implemented, and the measurement results agree well with the full-wave electromagnetic simulated responses.

Compact dual-band semi-lumped bandpass filter with LTCC technology

A novel low-temperature co-fired ceramic (LTCC) dual-band bandpass filter with compact size is reported. By using three semi-lumped resonators, not only the upper passband frequency can be conveniently tuned, but also the transmission zeros generated between the two passbands can be easily controlled by the elements of each resonator. A 2.5/5.2GHz dual-band experimental filter has been designed and fabricated to verify the proposed design concept. Based on the vertically-folded structure and LTCC technology, the filter only occupies an area of 5.1×4.6 mm2.

Compact dual-band bandpass filter using octagonal split-ring resonators with side-coupled stubs

A compact dual-band bandpass filter using side-coupled octagonal split-ring resonators (SRR) is introduced in this letter. The proposed filter employs two sets of SRRs operating at different frequencies to generate two passbands. Besides, the side-coupled stubs provide sufficient degrees of freedom to control the bandwidth of the two passbands. Four transmission zeros can be created close to passband edges which leads to high skirt selectivity. Measured results are in good agreement with the EM simulation results. The circuit size of the proposed filter occupies only 22.4 × 12.6 mm2 (≈0.25 × 0.14 λg). © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1169–1171, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25938

Dual-band bandpass filter using stepped-impedance stub-loaded hexagonal stepped impedance resonator (SIR)

In this article, a series of compact dual-band bandpass filters are proposed using the stepped-impedance stub loaded hexagonal stepped-impedance resonator. The resonator has three functions in the filter as follow: (1) dual-resonances operation introduced by the first- and second-resonance modes to dominate two passbands, (2) independent control of the operated frequencies of both passbands, (3) flexible configuration of the resonators implemented-scheme for specific bandwidth requirement. Then, based on the proposed resonator, two dual-band bandpass filters with wide- and narrow-passbands are fabricated, respectively. Good agreement between the measured and simulated results demonstrates the design feasibility of the dual-band bandpass filters. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1147–1150, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25894

Compact dual-band bandpass filter using open loop resonator loaded by in-line beeline for wideband applications

In this paper, a dual-band bandpass filter with low insertion loss in the pass bands and compact size is designed using only two open-loop microstrip resonators loaded by in-line beelines. The in-line beelines, are loaded to achieve two passbands with high performance. By adjusting the stub lengths and widths and also the tap line position, the harmonics above the second band are supperssed. The minimum insertion loss is 0.9 and 0.2dB at the first and second passbands respectively. The minimum attenuation above the second passband is -19.5dB from 5.4 up to more than 20GHz, so it can be used for wideband applications. This filter is then fabricated and measured. The measured and simulated results are in good agreement.

Compact dual-band bandpass filter with ultra wide stopband using open-loop resonator loaded by T-shape and open stubs

We present the design of a compact dual-band bandpass filter using open-loop resonator, which connected together with mixed coupling, loaded by T- shape stub and open stubs. Open stubs are loaded to achieve high performance and the tapped line feed structure is used in input-output port. By adjusting the tapping position, stubs length and the impedance ratio of T- shape stub, the filter performance can be controlled. The T shape stubs are used to suppress the harmonics above the second band. The insertion losses are 0.2dB and 0.9dB at 2.7 and 5GHz respectively. Above the second pass band minimum attenuation is -20dB from 5.3 to 20GHz, so it can be used for ultra wide stopband applications. The measurement results have shown a good agreement with the simulation.

Tunable electromagnetic band gap-embedded multimode resonators for ultra-wideband dual band, lower-ultra-wideband and upper-ultra-wideband applications

Three ultra-wideband (UWB) microstrip band-pass filters (BPFs) are proposed using tunable electromagnetic band gap (EBG)-embedded multiple-mode resonator (MMR) and fork resonator. In the first case, a compact dual-band BPF is implemented using a cascade of a multimodal fork resonator with tunable EBG. The fork resonator forms the basic structure yielding multiple band-pass realisations and the EBG selects the desired bands. This yields a compact dual-band BPF with sharp cut-off characteristics, wide bandwidth and low insertion loss. In the second case, a lower UWB filter is proposed by tuning an EBG-embedded MMR with parallel coupled microstrip line. Open circuited coupling stubs are introduced within the EBG structure to suppress higher order pass bands. In the third case, an upper UWB BPF is proposed in a similar manner as the lower UWB filter. However, the EBG-embedded MMR structure and the coupling technique are different. It is shown that the measured results are well matched to the predicted ones in terms of insertion/return losses over the plotted frequency range of 0.1–20.0 GHz. All simulations were performed with advanced design system (ADS) momentum (2.5D method of moments).

Compact dualband bandpass filter with two transmission zeros using dual‐mode microstrip resonator and tapped‐line geometry

AbstractIn this article, the dualband bandpass filters (BPFs) using dual‐mode resonator are designed and implemented. Also, the J‐inverter is investigated as function of the impedance and the electrical length of the open‐stub in the dual‐mode λg/2 microstrip resonator. Especially, the dualband BPFs using dual‐mode resonator are realized by the stepped impedance resonator (SIR) structure and have good out‐of‐band performance as the inverter is alternating by the coupling structure and tapped‐line geometry. The first transmission zero of the dualband BPFs is made by the dual‐mode resonator and the second transmission zero is defined by the open‐stub of the tapped‐line geometry as a function of J‐inverter. The dualband BPF using dual‐mode resonator with two transmission zeros shows the insertion losses of 1.92 and 1.71 dB at the center frequency of 2.42 and 5.65 GHz, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:108–111, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25627

Compact dual-band bandpass filter based on stepped impedance resonators and T-shaped line

A compact dual-band bandpass filter (BPF) realized with stepped impedance resonators (SIR) and T-shaped line is proposed in this article. By appropriately selecting the impedance ratio of the SIR, a passband around at 5.4 GHz can be achieved by the second harmonic frequency of the SIR. In addition, a T-shaped line is used to replace the quarter-wavelength line between the two SIRs, and another passband at 2.45 GHz is realized between the transmission zeros created by the central open stub of the T-shaped line and the fundamental frequency of the SIR. Moreover, the transmission zeros created by the central open stub and SIR could also be used to improve the skirt selectivity of the proposed BPF. Good agreement can be observed between the measured and simulated results, demonstrating the validity of the design strategies. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2721–2724, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25599

Compact Dual-Band Bandpass Filters Using Novel Embedded Spiral Resonator (ESR)

Compact dual-band bandpass filters (BPFs) are proposed using the novel embedded spiral resonators (ESRs) in this letter. Each ESR consists of two sets of spiral-lines embedded in a microstrip rectangular open-loop (MROP). The resonator has two functions in the filter: 1) dual-resonance operation mainly provided by the spiral-lines is employed to generate two passbands simultaneously. 2) MROP acting as the dual-feeding structure is introduced to achieve good input/output (I/O) coupling for both passbands. With proper tapping scheme, additional transmission zeros can be obtained to improve the passband selectivity. To verify the principle above, two dual-band BPFs are implemented. These filters with passbands operated at 2.4/5.2 GHz and 2.45/5.7 GHz can finely meet the wireless local area network (WLAN) bands requirements, respectively.

Compact dual-band bandpass filter using slot-line resonator

This letter presents a novel compact dual-band bandpass filter (BPF), which consists of two pairs of half-guided wavelength slot-line resonators. The two pairs of resonators, operating at different frequencies, generate two passbands for the proposed BPF by utilizing a novel coupling scheme. Tight coupling between the two resonators in each of the pairs can be simultaneously achieved, and the interaction between the two pairs is negligible. Thus the operation frequencies of the two passbands can be controlled independently. Several attenuation poles are created to enhance the selectivity of the proposed filter. The simulated and measured results are presented, showing good agreement. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2299–2300, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25485

Dual-Band Bandpass Filter Using Parallel Short-Ended Feed Scheme

In this letter, a compact dual-band (DB) bandpass filter based on parallel short-ended feed scheme is presented. Two sets of quarter-wavelength resonators operating at diverse frequencies are adopted to generate DB responses. A special feed scheme is proposed, which consists of two parallel short-ended strip branches. Each of them acts as a feed line of the respective resonator at one passband and a loading element at the other one. This scheme provides two independent transmission paths for RF signals. It is convenient to control the center frequencies of one passband, while the other's remains unchanged. Source-load coupling is also employed to create four transmission zeros close to the passband edges, resulting in high skirt-selectivity. To verify the proposed idea, a topology is demonstrated. The measured results exhibit good agreement with the full-wave simulation results.

The compact 3‐stage 2.4/5.2 GHz bandpass filter with modified winding hairpin structure and insert coupling

AbstractTwo hairpin resonators, one “Z‐type” modified stepped‐impedance resonator, and two transmission lines are composed to design the compact and miniature dual‐band bandpass filters (BPFs).The designed BPFs are presented to operate at 2.4/5.2 GHz for industrial, scientific, and medical (ISM, 2.4 GHz) and WLAN applications (2.4/5.2 GHz) without additional impedance matching network. The 2.4 GHz and 5.2 GHz dual‐band can be simultaneously excited and tuned by adjusting the electric length ratio (θ) and characteristic impedance ratio (K) of resonators. Cascaded arrangement is designed for wide bandwidth and high out‐of‐band rejection, and the “Z‐type” resonator and insert coupled modification are used to increase the utility rate of space and reduce the size of designed filter. Al2O3 ceramic with thickness of 0.635 mm and dielectric constant of 9.4 used as the substrate, and the designed filters are fabricated by printing method. Because of higher dielectric constant substrate and modified structure, the proposed filters show the advantages of wide bandwidth, low insertion loss, high out‐of‐band rejection, simple circuit, and tiny size. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1156–1159, 2010; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.25128

Develop compact dual‐band bandpass filters on the aluminum oxide

AbstractFor the purpose of minimizing the dual‐band bandpass filters (2.4 and 5.7 GHz), two stepped impedance resonator structures are modified and involved in a pair of distorted coupled lines to form a compact structure.And because the designed filter is printed on the high quality factor and dielectric constant aluminum oxide ceramic substrate by the screen‐printing technique, the characteristics of the filters could be improved and the size of the filters could be minimized to only 22.2 × 12 mm2. Furthermore, the modified SIR structure can be used to tune the second resonant frequency (harmonic) for the applications of dual bands, and the modified coupled line structures can be used to excite additional transmission zeros and adjust its locations, which can improve the characteristics of the filters effectively. In this article, the optimum measured insertion loss and bandwidth for 2.4 GHz are −0.98 dB and 11.1%, respectively, and for 5.7 GHz are −1.05 dB and 10.1%, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1091–1094, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25126

A DUAL-BAND BANDPASS FILTER HAVING WIDE AND NARROW BANDS SIMULTANEOUSLY USING MULTILAYERED STEPPED IMPEDANCE RESONATORS

Compact dual-band bandpass filter (BPF) with wide and narrow bands simultaneously is presented. By using the stepped impedance resonators (SIRs) in multilayered structure, the dual-band responses with wide and narrow bands simultaneously can be obtained. The filter has 3-dB fractional bandwidths (FBWs) of 45% and 10% for 2.4GHz and 5.2 GHz, respectively. The circuit size is compact due to the multilayered structure. Moreover, multi-path propagation inside the multilayered structure generates transmission zeros at each skirt of the passbands for improving the passband selectivity. Measured results of the filter are in good agreement with the full-wave electromagnetic (EM) simulation. Corresponding author: H.-W. Wu (qqq25q@gmail.com).

Compact dual-band bandpass filter using defected microstrip structure for GPS and WLAN applications

A modified defected microstrip structure (DMS) for designing a dual-band bandpass filter with independently controlled centre frequencies is presented. The DMS using an F-shaped spurline embedded into a uniform impedance resonator is applied to generate double-resonance characteristics. Based on this theory, a dual-band filter for GPS/WLAN applications has been designed, analysed and fabricated. It is compact and has easy fabrication. Measured results verify the validity of this design methodology. Also, this is believed to be the first report on the DMS in microwave dual-band filter design.

A Compact Dual-Band Bandpass Filter with High Band Selectivity using Cross-Coupled Asymmetric Sirs for Wlans

In this paper, we have proposed the design of novel compact dual-band bandpass filter (BPF) with high band selectivity by using only two asymmetric stepped impedance resonators (SIRs) with one step discontinuity. By arranging the cross-coupled SIRs, three transmission zeros near the passband edges and a high isolation between two passbands are introduced to improve the band selectivity of the proposed filter. The dual-band frequencies of this BPF is implemented by properly selecting the impedance ratio (R) and physical length ratio of the asymmetric SIRs. The bandwidths and the coupling coefficients of the two passbands (2.4/5.2 GHz) can be designed by adjusting the coupling gap between the resonators. The proposed BPF has a smaller circuit size in comparison with previous works using conventional direct-coupling SIRs. The measured results are in good agreement with the full-wave simulation ones.

Compact Dual-Band Bandpass Filter Using Asymmetrical Dual Stub-Loaded Open-Loops

A compact dual-band bandpass filter is proposed using asymmetrical dual stepped-impedance stub-loaded open-loop resonators, where additional transmission zeros are introduced so as to improve its upper rejection. Its mode characteristics and generation of its transmission zeros are analyzed theoretically. In such a filter, double resonators have different configurations, with their individual transmission zeros generated at different frequencies. It is demonstrated that the realized filter has good performance in frequency selectivity and spurious suppression. Also, good agreement is obtained between its simulated and measured S-parameters. Its –20 dB upper stopband is improved up to 2.57 times of the first central frequency, which is much better than its previous dual-band counterparts with small frequency ratios.